It doesn't really run an OS like you may be used to. It runs FreeRTOS, which schedules tasks. One of the tasks is running Micropython. (Other tasks are for audio, the display, MIDI, touchscreen, the sequencer, etc). There's no BIOS-level code to use, we have to manage our own screen (including drawing in groups of scanlines at a time to save RAM.)
There are ways to write Rust code for the underlying MCU -- the ESP32-S3, but Tulip itself is Micropython with a lot of C glue code to handle the audio, display, UI, and MIDI. People that get a Tulip will be writing Python on Tulip, and Tulip itself is C + Python.
This is a pretty bespoke thing -- stuff made for an RPi / linux won't directly port over. It's running Micropython and has got custom code to handle the screen, there's no obvious framebuffer or terminal. But anything is possible and I bet you could take the bits of the firmware you need to port over your own stuff!
I work on this! AMA if you have any questions. I think it's really cool and has been fun to hack on. the main github w/ all the specs and code is at https://github.com/shorepine/tulipcc